As semiconductor chips are minimized and highly integrated, one of more advanced packages is a multi chip package (MCP). The MCP is a technique in which an additional chip is mounted on a chip, so that the MCP makes it possible to allow much more components to be mounted in a package with the same size in comparison to a prior art.
In the MCP method, bonding between a semiconductor chip and a semiconductor substrate is made using a film-shaped adhesive, instead of existing liquid epoxy paste (Japanese Laid-open Patent Publication H3-192178 and H4-234472). A method using a film-shaped adhesive includes a film component adhesion method and a wafer backside adhesion method. In the film component adhesion method, a film-shaped adhesive is cut or punched into a piece suitable for the chip and then adheres to a semiconductor substrate. Thereafter, the chip is picked up from the wafer, a die bonding is performed thereon, and then a semiconductor device is prepared through post-processes such as wire bonding and molding.
On the other hand, in the wafer backside adhesion method, one side of a film-shaped adhesive is attached to a backside of a wafer, and a dicing tape having a tacky layer is additionally attached to the other side of the film-shaped adhesive, which does not adhere to the backside of the wafer, so that the wafer is diced into individual chips. The separated chip is picked up and die-bonded to a semiconductor substrate, and then it is made into a semiconductor device through wire bonding and molding. The wafer backside adhesion method has difficulties in conveyance of a thin wafer, increased process number, adaptability for various chip thicknesses and sizes, film thinning, and reliability of high-functional semiconductor device.
In order to solve the above problems, there have been proposed methods in which a film having adhesive agent and tacky agent in one layer adheres to a backside of a wafer (Japanese Laid-open Patent Publication H2-32181, H8-53655 and H10-8001). Such methods do not require two lamination processes but requires only one lamination process, and also a wafer ring for supporting a wafer is provided, so that there is no problem when the wafer is conveyed. According to the above documents, a dicing die bonding integrated film composed of a substrate and a tacky/adhesive agent made of a specific composition includes a radiation-curing tacky agent and a thermosetting adhesive agent in mixture. This adhesive agent plays a role of a tacky agent in a dicing process, and then loses its tacky power through a radiation-curing process to facilitate picking-up of the chip from the wafer. Also, the adhesive agent is thermoset as an adhesive agent in a die-bonding process, so that the chip is firmly adhered to a semiconductor substrate. However, tacky power of the dicing die bonding integrated film is not sufficiently lowered after radiation curing, so that the chip may not be easily separated from a substrate during a semiconductor chip pick-up process after the dicing, which may cause inferiorities.
In order to solve the problem of the integrated film, there has been proposed a dicing die bonding separation film composed of two layers of tacky layer and adhesive layer such that it may be used as a dicing tape in a dicing process and also used as an adhesive agent in a die bonding process. Since the tacky layer and the adhesive layer are easily separated by heat or radiation curing after the dicing process, the dicing die bonding separation film does not cause any problem during the semiconductor chip pick-up process, and also may conveniently allow thinning a thickness of the film during the die bonding process. Due to the above advantages, film-shaped adhesives are more frequently used in an actual packaging process although they have problems in filling-up when adhering to a semiconductor substrate, in comparison to existing liquid epoxy.
However, such dicing die bonding separation film has a multi-layered structure, so that burr is generated due to severe external conditions occurring in a dicing process due to difference in property between the layers. Thus, in order to apply the dicing die bonding separation film to a semiconductor chip, which is directed to smaller and thinner design, with high reliability, it is urgent to develop a method for ensuring balanced properties between layers in addition to basic properties of the dicing die bonding film and thus minimizing burr.